The dream of a universal history of astronomy

 

While crossing Germany towards Saint Petersburg, Delisle builds relationships with German scientists and manages to purchase several precious documents, among which Johannes Hevelius' letters. From then on, he would keep on collecting letters and manuscripts from well-known authors : Tycho Brahe, Kepler, La Hire and many others. But his project is not only a collector's one. He likes to recall that the study of the history of sciences, "which is only useful or pleasant in some sciences, becomes absolutely necessary in astronomy ; since this science is grounded on nothing but the observations of diverse times and different places, of which no astronomer could make any use without distinguishing exactly these times and places ; nor without looking carefully for the aim with which these observations were made and the degree of knowledge one had in those days." [1] He therefore accumulates biographical notes on the astronomers of the past, and corresponds regularly with whoever is able to convey him knowledge on these topics. [2]

 

Dessin d’une machine astronomique pour expliquer le mouvement des comètes inventée par Martin Knutzen

Passing through Königsberg on his way back to France, Delisle makes this drawing, from memory, of a machine to observe the stars designed by Martin Knutzen, a philosopher follower of Wolff and a professor who initiated Kant into Newtonian mechanics.

 

 

Notice sur Thalès de Milet

an illustration of Delisle's encyclopedic interests : the notice he devotes to Thales, "the first among the Greeks to predict the solar eclipse [...]"

By collecting this huge amount of data, Delisle clearly intended, as he explained in the preface to a collection of 1738, "to compose a complete treatise on astronomy, historically expounded, & demonstrated by all the observations made up to now".  Yet, having realised the excessiveness of such an ambition, he admitted that he had to revise it downwards : " [...] I understood in the end [...] that this project was beyond reach, or at least that it was uncertain whether I would manage to achieve it alone." He thus opted for a partial publication, in the form of "specific mémoires", leaving to his successors the task "to compose a history and a complete treatise on astronomy out of them in the future [...]." [3]

 

 

 


[1] abrégé de l’histoire des observations astronomiques que j’avais préparé pour lire à l’assemblée publique de l’académie de Petersbourg le 2 mars 1728, Delisle collection (Observatoire de Paris), portfolio A7/10, piece 8.

[2] Aware of the value of these archives, Louis XV offered Delisle to trade them for a pension of 3000 livres and the title of astronomer of the Navy. They are kept in the archives of the Navy until 1795, when the Committee of Public Safety tranfered the astronomical part of them to the Bureau des Longitudes, the institution created on the same year to manage Paris Observatory.

[3] Mémoires pour servir à l’histoire & au progrès de l’astronomie, de la géographie & de la physique. Besides, we could think, following Nina I. Nevskaja, that Delisle was not expecting too much of his followers : « Actually, she wrote, the work Delisle started was completed by his students J.-J. Lalande (1732-1807) and N.-L. Lacaille (1713-1762) who published a series of studies on the history of astronomy. Two students of Lalande, J.-S. Bailly (1736-1793) and J.-B. J. Delambre (1749-1822), continued this tradition. Delisle's ideas on astronomical motivations in mythology and religions were developped in the works of another student of Lalande, Ch.-F. Dupuis (1742-1809). Scientific and historical studies by François Arago (1786-1853), a student of Delambre, are very well-known. They all follow the path set forth by Delisle and make extensive use of materials from his collection. » (op. cit., p. 293-294)